DESCRIPTION (Adapted from applicants abstract): The overall goal of this project is to investigate the cellular processes that underlie two forms of associate learning - classical conditioning and operant conditioning. Studies will focus on consummatory feeding behavior of Aplysia. This behavior can be modified by both classical and operant conditioning. Moreover, many key elements of the neural circuitry have been identified and this circuitry retains many of its functional characteristics in vitro. The project has four specific aims: First, investigate cellular mechanisms underlying an in vitro analogue of operant conditioning. As a first step toward a cellular analysis of operant conditioning, we developed a preparation that retained the essential features of operant conditioning in vitro and was amenable to cellular analyses. The first aim is to identify and characterize the neuronal plasticities underlying this analogue of operant conditioning; identify cells and/or transmitters mediating the reinforcement; and investigate the cellular mechanisms encoding the temporal specificity of contingency-dependent neuronal plasticity. Second, develop an in vitro analogue of classical conditioning. To facilitate the cellular analysis of classical conditioning, we will develop an in vitro preparation that retains the essential features of classical conditioning and that is amenable to cellular analyses. The second aim is to characterize pathways mediating the reinforcement; to establish a stimulation protocol that mimics classical conditioning; and investigate cellular mechanisms underlying this in vitro analogue of associative learning. Third, identify neuronal correlates of classical and operant conditioning. Although the in vitro analogues may retain the essential features of associative learning, these reduced preparations are removed from the behaving animal. Thus, it is critical to explore loci and changes in the nervous systems of animals that have been behaviorally trained. The third aim is to determine whether the cellular loci that are modified by the in vitro analogues of associative learning (both classical and operant conditioning) are also modified by behavioral training; and to determine whether behavioral conditioning involves additional cellular loci. Fourth, compare cellular processes mediating short- (1 hr), intermediate- (~4 hr) and long-term memory (24 hr). The forth aim is to characterize and compare different temporal domains of memory that are induced by classical and operant condition; identify neuronal correlates for each phase of memory; and for each domain of memory, develop an in vitro analogue that will be amenable to cellular analyses. The proposed studies will provide the first major insights into the cellular mechanisms that underlie operant conditioning, as well as provide an opportunity for a mechanistic comparison of classical and operant conditioning.